This application is based on Japanese Patent Application No. 10-108119, filed Apr. 17, 1998, the contents of which are incorporated herein by reference.
In recent years, along with advance of the computer technology, various kinds of multimedia compatible electronic devices such as digital video players, set-top boxes, TVs, personal computers, and the like have been developed.
Such electronic device can play back digital contents such as a movie stored in a DVD (Digital Versatile Disk), a TV program transmitted by a digital satellite broadcast, and the like.
It is a common practice to encode digital contents by moving image high-efficiency coding called MPEG2, and to then send them to homes via recording media or transmission media. MPEG2 coding is based on the principle of variable rate coding to assure both high image quality and a short recording time in relation to the capacity. The volume of data encoded by variable rate coding depends on the image quality of a source image, and increases as the scene includes faster motions. Hence, digital contents can provide a video with image quality as high as an original video.
Recently, in view of protection of the copyrights of such digital contents, the need for copy protection techniques for preventing their illicit copies has been advocated, but no effective schemes have been configured yet.
For this reason, CPTWG (Copy Protection Technical Working Group) is now preparing for new copy protection specifications designed for an IEEE1394 serial bus as the next-generation bus interface suitable for multimedia data transmission (to be referred to as an IEEE1394 copy protection technique hereinafter).
The IEEE1394 serial bus is the next-generation bus interface, which connects a digital video player, set-top box, TV, personal computer, and the like, and supports two different transfer modes, i.e., an asynchronous subaction and isochronous subaction. The former mode is called an asynchronous transfer mode, and is used upon transferring data that does not require real-time processing. The latter mode is an isochronous transfer mode that guarantees a transfer band, and can transfer digital contents represented by video data and audio data in real time.
As the IEEE1394 copy protection technique, digital contents which are exchanged among devices such as a digital video player, set-top box, TV, personal computer, and the like via the IEEE1394 serial buses may be enciphered or encrypted using known enciphering techniques such as a public key system, common key system, and the like so as to prevent their illicit copies.
However, since a personal computer is by nature an open system, satisfactory protection against illicit copies cannot be expected by merely enciphering data that flow on the IEEE1394 serial bus.
More specifically, if an enciphering/deciphering function is provided to a 1394 bridge in a personal computer, the open architecture of a PCI bus can be maintained, but deciphered data (plain contents) flow on the PCI bus and can be easily copied.
For this reason, a new system that can encipher digital contents transferred on the PCI bus must be built.
However, when such system is built, since the copy protection technique for digital contents basically limits transfer (copy) of the entire stream data made up of digital contents in correspondence with the type of digital contents (copy once, copy never, copy freely), it is impossible to realize flexible control for partially limiting digital contents that can be handled in correspondence with their contents.
Like in DVD, it is recently required in transfer control of stream data to impose limitations not only on the entire stream data but also on its portion. For example, transfer is granted only when a condition set by the user is satisfied (parental control) or in a predetermined region (region control).
However, parental control or region control in DVD is implemented by setting in advance a branch structure in a title recorded on a DVD medium. Hence, no problem is posed in case of a system which can individually designate data contents to be provided in units of users, but such control cannot be applied to a system which must transmit an identical stream to many unspecified persons such as stream data of a TV program of a satellite broadcast.
It is an object of the present invention to provide a data processing system which can flexibly control limitations on stream data that can be dealt with, and a stream data limiting method applied to the system.
In order to achieve the above object, according to the present invention, in a stream data processing system for receiving and processing stream data, field data indicating a field of contents contained in the data stream is embedded in a header field of a data packet that forms the stream data, and the system comprises limiting means for controlling grant/denial of processing of the stream data in units of partial data that make up the stream data on the basis of the field data contained in the received stream data.
In this stream data processing system, by checking a coincidence or the like between field data embedded in the header field of a data packet and that set in advance in the system by the user, grant/denial of processing can be partially controlled in correspondence with the contents in stream data in place of limiting the entire stream data. Hence, each receiving system can flexibly control the contents that the system can deal with without requiring any control for changing the stream to be transmitted in accordance with the branch structure of a title. For example, even when the present invention is applied to stream data for a digital broadcast such as satellite, ground wave, cable TV, and the like for many unspecified persons, flexible limitations on processing data can be easily realized.
In place of or in addition to the field data, region data for specifying a region where the contents can be used may be embedded in the packet header field.
When the present invention is applied to a system which protects the copy right of digital contents by enciphering and exchanging stream data between a plurality of devices, control that allows a receiving device to process only contents of a type which matches the field or region designated by the user among the types (copy once, copy never, copy freely) of digital contents that the receiving device can deal with can be made. In this way, for example, when stream data for a digital broadcast is recorded on a device such as a digital VCR or the like, the recording contents can be limited.
As described above, according to the present invention, grant/denial of processing can be partially controlling on the basis of region or field data embedded in the header field of a data packet in place of limiting the entire stream data. Consequently, contents that each receiving system can deal with can be flexibly controlled without requiring any control for changing the stream to be transmitted in accordance with the branch structure of a title. For example, even when the present invention is applied to stream data for a digital broadcast such as satellite, ground wave, cable TV, and the like for many unspecified persons, flexible limitations on processing data can be easily realized.
When the present invention is applied to a system which protects the copy right of digital contents by enciphering and exchanging stream data between a plurality of devices, control that allows a receiving device to process only contents of a type which matches the field or region designated by the user among the types (copy once, copy never, copy freely) of digital contents that the receiving device can deal with can be made. In this way, for example, when stream data for a digital broadcast is recorded on a device such as a digital VCR or the like, the recording contents can be limited.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.